A plume of exhaust rises from the Mitchell Power Station, a coal-fired power plant located in New Eagle, Pa., on Sept. 24, 2013.

No one knows for sure how much President Obama will call for reducing carbon emissions from existing power plants when he unveils a new EPA rule next week, but Morgan Stanley analysts believe this: It’ll be more than 17%.

Critics of the reduction received some ammunition from the Morgan Stanley report, which points out that the impact on coal demand would be “substantial” in the long term if the proposal goes above the Copenhagen carbon-reduction target.

Back in 2009, Obama called for a 17% reduction in emissions from 2005 levels by 2020, ahead of climate talks in Copenhagen.

The coming new regulation is already being bashed by the coal industry, the U.S. Chamber of Commerce and politicians from both parties. The charge is it will raise electricity costs and destroy jobs.

Fast forward five years, and the analysts said in a Thursday note the new EPA rules – expected Monday – will be “in excess” of that target. (The New York Times reported Obama will use his authority to cut emissions from coal-fired power plants by up to 20%, in turn spurring the creation of a state cap-and-trade program.)

The Morgan Stanley analysts believe the rule would go into effect in 2018 at the earliest. And that’s assuming lawsuits don’t get in the way first.

To achieve Obama’s carbon emissions goals, the analysts write, the EPA will need to make a broader interpretation of the Clean Air Act. “This broader approach would, in our view, invite a significant amount of litigation,” they say.

If what Obama proposes isn’t much above the Copenhagen target, the industry itself might not feel much of a bite. As the report points out, lower coal-plant output has already cut U.S. power-sector carbon dioxide emissions by about 11% in the 2005 to 2011 period.